Automotive electrochromic mirror reflective element cell assemblies typically include a front substrate and a rear substrate and an electrochromic medium sandwiched therebetween and contained within an interpane cavity. The substrates are shaped as desired by the automobile manufacturer for a particular mirror design or application. For example, an interior rearview mirror reflective element may have substrates that are generally oval or trapezoidal in shape and are formed to be approximately 20-26 cm long and 5-8 cm tall or wide. Exterior mirror reflective element assemblies are shaped differently and may have sharper radii at the corners and may be flat or convex or aspheric, depending on the particular application. The size of the substrates for the exterior reflective element assemblies may vary from about 7 cm by 7 cm to about 10 cm by 18 cm or larger.
During manufacture and assembly of the reflective cell element assembly, the respective front and rear substrates are often cut or broken out as cut shapes from larger flat or curved lites, typically glass sheets or lites. The individual front and rear cut shapes or substrates are cleaned and then coated with a conductive or semiconductive coating or coatings that are reflective or transparent. After they are coated, an uncured adhesive material, typically an uncured epoxy material (often containing spacer beads, such as glass beads or the like), is applied around the perimeter of one of the cut shapes or substrates, and polymethylmethacrylate (PMMA) beads are added at the substrate and inboard of the epoxy material, and the other cut shape or substrate is superimposed thereupon and spaced apart from the first cut shape by the applied perimeter material. The uncured adhesive material is then cured, such as by heating, to adhere the shapes or substrates together and to space the substrates apart a desired or appropriate or selected amount to define an appropriate interpane cavity spacing. The substrates, so adhered together and interspaced apart, form an empty cell with an interpane cavity between the substrates and bounded by the perimeter seal.
Next, an electrolyte or monomer composition is filled into the cavity via an aperture (commonly known as a fill port or plug hole) provided in the perimeter material or seal, such as via a vacuum fill process. During the filling process, the interpane cavity is in a vacuum and the empty cell is disposed in a vacuum chamber. Thus, when the fill port is placed in a source of electrochromic fluid, and the chamber is pressurized or vented to atmosphere, the fluid is drawn up into the vacuumed interpane cavity to fill the cell. The beads in the interpane cavity are required, at least for larger cells, to avoid collapsing of the cell when the chamber is at a higher pressure than the interpane cavity. After the cell is filled and the port is plugged, the cell may be heated to dissolve the beads, and the cell is cleaned to remove the electrochromic fluid that is present at the surface of the cell and around the fill port.